Influence of substrate bias on the structure and properties of TiCN films deposited by radio-frequency magnetron sputtering

The aim of this paper is to investigate the effects of the substrate bias on the structure and properties of the TiCN thin films. The TiCN films were grown onto silicon and steel substrates by rf reactive magnetron sputtering from a pure titanium target in Ar-CH4-N-2 gas mixture. Various techniques (such as X-ray diffraction, Raman spectroscopy, energy dispersive X-ray spectroscopy, nanoindentation and potentiodynamic polarization) were used to analyze the structure, phase composition, mechanical properties, and corrosion-resistance of TiCN films. Additionally, the friction and wear properties of TiCN films were investigated by sliding them against alumina ball in the air. Experimental results of the deposition rate showed a decrease from 31 nm/min to 9 nm/min at biased substrate voltage from Vs = 0 to - 100 V respectively. The refractive index for the TiCxNy films was between 2.10 and 2.26, while the roughness of the films ranged from 142 nm and 42 nm. The film deposited at 0 V was amorphous, while films at other bias voltages have a face-centered cubic structure (like NaCl type) with a preferential growth orientation of (111). It was observed that Ti and C contents increase from 38 to 52 at.% and 25 to 36 at% respectively, as a function of increasing bias voltage. The results also indicate that TiCN films deposited at a substrate bias voltage of -70 V had a maximum hardness of 39 GPa, and exhibited better wear resistance, with minimum wear rate and lower coefficient of friction of 0.13. The hardness significantly increased from 16 to 39 GPa when the bias voltage was increased from 0 to -70 V and then slightly decrease to 38 GPa as further increased to -100 V. The minimum corrosion current density of the film was 0.0205 mA/cm(2) for films deposited at -70 V, which is about five times less than that of the uncoated steel (0.1140 mA/cm(2)). (C) 2016 Elsevier B.V. All rights reserved.